Study on optimization of water-cement ratio of the cement grout for sealing boreholes in gas drainage

In order to further improve the accuracy of borehole sealing simulation for gas extraction in the coal seam, considering the influence of viscosity time-varying and stress on the grout diffusion during the diffusion of cement grout, laboratory tests were conducted to measure the basic properties of cement grout with different water-cement ratios, and the performance and variation characteristics of cement grout with different water-cement ratios were analyzed. Through theoretical deduction and numerical simulation, the cement grout diffusion range under different water-cement ratios were studied and calculated, and the water-cement ratio for grouting and sealing boreholes in coal mine were optimized. The simulation results in Xiaotun Coal Mine in Guizhou showed that the sealing effect was good, which further optimized the water-cement ratio of cement grout based on the actual conditions of the mine. The results show that the initial dynamic viscosity of cement grout decreases with the increase of water-cement ratio, and the viscosity of cement grout increases exponentially with time; according to the actual sealing borehole situation and the simulation results, the optimal water-cement ratio of cement grout is 0.9.